Herbicides which demonstrate potent total vegetation control over a broad spectrum of annual and perennial weeds are of high interest in agricultural practice. Accordingly, there is an ongoing search in the art to discover new and effective herbicides. (+)-Hydantocidin, produced from Streptomyces hygroscopicus which was isolated from a soil sample collected in Japan, has demonstrated herbicidal activity at levels comparable to commercial standards such as glyphosphate and bialaphos and has also been shown to be non-toxic to mammals (c.f. Nakajima, M.; Itoi, K.; Takamatsu, Y.; Kinoshita, T.; Okazaki, T.; Kawakubo, K.; Shindo, M.; Honma, T.; Tohjigamori, M.; Haneishi, T. Journal of Antibiotics 1991, 44,293.).
The use of (+)-hydantocidin as a herbicide is described in U.S. Pat. No. 4,952,234. A process for the preparation of said compound is described in DE 4,129,728. Two complimentary syntheses of (+)-hydantocidin are Mio, S.; Ichinose, R.; Goto, K.; Sugai, S. Tetrahedron 1991, 47,2111 and Mio, S.; Kumagawa, Y.; Sugai, S. Tetrahedron 1991, 47,2133. However, all of these processes are fundamentally similar and are not economically feasible. In general, many synthetic transformations are required, overall yields are low, and chemical selectivity is lacking.
It is, therefore, an object of the present invention to provide a simple and efficient enantioselective process for the preparation of (+)-hydantocidin.
It is another object of this invention to provide intermediate compounds useful in the preparation of hydantocidin and derivatives thereof.
It is a further object of this invention to provide thiohydantocidin compounds which are useful as herbicidal agents.